Today’s Wonder of the Day was inspired by Rebecca. Rebecca Wonders, “What does it mean when a planet is in retrograde?” Thanks for WONDERing with us, Rebecca!
Humans have looked to the night sky for thousands of years. In doing so, we’ve found many interesting patterns. Today, we can predict eclipses and meteor showers. We know about the paths of comets and galaxies. This Wonder of the Day is about another pattern of movement you may have heard about—retrograde.
What is retrograde? It has to do with the movement of planets. You probably already know that all the planets in our solar system orbit the Sun. That’s where they got their name—the Greek word planetes, which means “wanderer.”
From Earth, we can observe the orbits of the other planets. Usually, they appear to move in the same direction. If you map their movements night after night, though, you’ll see that they sometimes seem to reverse their path. This is called retrograde.
What happens when planets are retrograde? Are they lost? Taking a detour? Tired of their same old orbit? No, of course not! There is a scientific explanation for retrograde. It just took researchers many years to find it.
Remember that all the planets in our solar system travel at different speeds. Those closest to the Sun orbit faster than those farther out. That’s why the length of a year is different on every planet. For example, one year is 88 Earth days on Mercury and 687 on Mars.
For that reason, planets will sometimes lap each other in orbit. Planets closer to the Sun will pass their slower-moving neighbors. For example, Mercury laps Earth about three times a year. Earth does the same to Mars every two years.
As the planets pass each other, it causes an optical illusion. From Earth, it looks like the other planet changes direction. However, both planets are actually still moving the same way—retrograde is just the illusion we see.
Still, some people think there’s more to the story. In astrology, retrograde is said to affect life on Earth. For example, many people dread Mercury retrograde. Why? They believe Mercury is linked to communication. As such, they say Mercury retrograde can impact communication and relationships.
That’s just one example. Every planet in the solar system is retrograde at one time or another. Each one is said to affect people differently—even if there is no scientific proof.
Have you ever noticed strange effects during retrograde? What other space topics are you curious about? It’s so much fun to learn more about our universe!
Standards: NGSS.ESS1.A, CCRA.R.1, CCRA.R.2, CCRA.R.4, CCRA.R.10, CCRA.W.2, CCRA.W.4, CCRA.W.7, CCRA.W.8, CCRA.W.9, CCRA.L.1, CCRA.L.2, CCRA.L.3, CCRA.L.6, CCRA.SL.1, CCRA.SL.2, C3.D2.Geo.2